This invention relates in general to trunked communication systems, and more particularly to trunked communication systems employing signal voting.
Radio communication systems operating over a wide coverage area tend to be organized into geographic regions, each supported by a radio communication site. In a typical system, such as a trunked radio system, the communication sites are geographically dispersed and provide localized support for the transmission and receipt of wireless communication radio frequency (RF) signals for communication units, such as mobile and portable radio transceivers. Some prior art communication systems employ a simulcast broadcast methodology. Simulcast systems transmit identical messages from multiple communication sites, typically on the same communication channel, to increase a broadcast coverage region. Generally, these communication sites also function to receive transmissions from communication units for processing and possible retransmission.
A RF transmission from a communication unit may be received by multiple sites. Each site typically conveys received signals via a wired or wireless communication link to a controller site, which attempts to determine the original transmitted signal from the signals received through the various sites. Generally, the controller site assumes that signals received substantially simultaneously on a given radio frequency channel from the various sites are to be treated as originating from a single signal source via multiple signal paths. Many radio systems employ signal voters which reside at the controller site that receives the various signals from the receiving sites. A voter operates by selecting a signal from a receiving site which most likely represents a signal transmitted by the communication unit. Various methodologies have been employed within a voter to make this determination. For example, some systems select a transmission based on a received signal strength indicator (RSSI), which indicates the quality of the received signal based on received signal strength and/or other factors. The voter derives the best representation for the original signal transmitted, typically by selecting the signal received with the best signal quality.
FIG. 1 shows a typical prior art simulcast trunked radio communication system that employs voters as described above. The radio communication system 100 has an infrastructure which includes a controller 112, and signal voters 116, which support satellite sites 120 which having multiple operating RF channels. As in traditional systems employing voters, a voter 116 is provided for each operating RF channel. Each operating channel is coupled to a voter 116, such as by wired or wireless link. The controller 112 interfaces with the voters 116 to determine a preferred (or xe2x80x9cvotedxe2x80x9d) received signal for a particular operating channel, from versions of a signal received at multiple sites. The controller 112 also interfaces with the satellite sites for the transmission of signals, such as for simulcast operations.
There are certain problems associated with the typical prior art radio system configuration as depicted in FIG. 1. Generally, a dedicated voter per channel usually means that a particular channel is reserved throughout the system whenever that channel is used anywhere within the system. This limits the reuse of communication resources and imparts a rigidity in simulcast and other communication system operations. Additionally, when a voter experiences downtime, i.e., the voter is out of service, the use of that RF channel is precluded until the voter can be serviced.
It is desirable to increase the reliability and flexibility of radio communication systems incorporating satellite sites and signal voters. Therefore, there is a need for an improved approach to the design and implementation of such systems.